Researchers from the University of Utah contend that human faces – especially those of our prehistoric australopith ancestors – evolved in structure to minimize injuries from punches to the face between fighting males. The new study, published in the journal Biological Reviews on Monday, finds that modern human faces were more directly shaped by violence than previously long-held hypotheses have suggested.

University of Utah biologist David Carrier and physician Michael H. Morgan propose that fistfights between prehistoric males helped develop a more resilient, robust facial structure to take such punches.

“When modern humans fight hand-to-hand the face is usually the primary target. What we found was that the bones that suffer the highest rates of fracture in fights are the same parts of the skull that exhibited the greatest increase in robusticity during the evolution of basal hominins,” Carrier said in a statement.

“These bones are also the parts of the skull that show the greatest difference between males and females in both australopiths and humans. In other words, male and female faces are different because the parts of the skull that break in fights are bigger in males.”

Carrier and Morgan’s study, “Protective Buttressing of the Hominin Face,” note that these structural changes to the face occurred at the same time that human ancestors evolved hands with the proportions capable of forming a fist.

“Importantly, these facial features appear in the fossil record at approximately the same time that our ancestors evolved hand proportions that allow the formation of a fist,” said Carrier. “Together these observations suggest that many of the facial features that characterize early hominins may have evolved to protect the face from injury during fighting with fists.”

The study links the formation of the fist as weapon to the necessity of the face’s protection.

“The australopiths were characterized by a suite of traits that may have improved fighting ability, including hand proportions that allow formation of a fist; effectively turning the delicate musculoskeletal system of the hand into a club effective for striking,” said Carrier. “If indeed the evolution of our hand proportions were associated with selection for fighting behavior you might expect the primary target, the face, to have undergone evolution to better protect it from injury when punched.”

Research of the ape-like creatures in the genus Australopithecus – the immediate predecessors to the human genus Homo, who inhabited the earth about 4 to 5 million years ago – continues as scientists look into how and why humans evolved into their modern form.

The study also provides a more violent alternative to long-held theories suggesting that human ancestors evolved robust faces from a need to chew hard-to-crush foods such as nuts.

Carrier says that this study “provides an alternative explanation for the human evolution of the hominin face,” adding that it also “addresses the debate over whether or not our distant past was violent.”

“The debate over whether or not there is a dark side to human nature goes back to the French philosopher Rousseau who argued that before civilization humans were noble savages; that civilization actually corrupted humans and made us more violent,” said Carrier. “This idea remains strong in the social sciences and in recent decades has been supported by a handful of outspoken evolutionary biologists and anthropologists. Many other evolutionary biologists, however, find evidence that our distant past was not peaceful.”

But Carrier adds that coming to terms with humans’ violent behavior can assist modern humans to make peaceful changes.

“Our research is about peace. We seek to explore, understand, and confront humankind’s violent and aggressive tendencies. Peace begins with ourselves and is ultimately achieved through disciplined self-analysis and an understanding of where we’ve come from as a species. Through our research we hope to look ourselves in the mirror and begin the difficult work of changing ourselves for the better.”